1. Field of the Invention
This invention relates to a lateral-irradiation type laser irradiation device for curing ailing tissue by irradiating the affected region with a laser beam and a method for the therapy of prostate gland by the use of the laser irradiation device.
2. Description of the Prior Art
Some kinds of the laser irradiation device is used for curing an ailing tissue by inserting the device into a lumen such as the blood vessel, the urogenital canal, or the abdominal cavity and causing the device to emit an in-vivo deep reaching laser beam to the affected region.
This laser irradiation device, by making use of a relevant body cavity or by being inserted into a relevant part of the body through a small incision, cures a lesion by irradiating a laser beam of a varying energy density upon the site of the lesion thereby inducing degeneration, necrosis, solidification, cauterization, incision, or transpiration of the lesion.
This technique consists in directly irradiating the laser beam on the lesion located in or near the surface layer of the tissue. Recently it has become to be utilized also for curing a lesion located in the deep part of the tissue.
Since the laser beam is emitted at a relatively high output for the purpose of heating the lesion of this sort to an amply high temperature, it has the possibility of injuring the relevant surface layer of the tissue.
In the circumstance, therefore, an idea of providing the laser irradiation device at the distal end part thereof with a plurality of laser beam emitting parts and causing these emitting parts respectively to emit laser beams in a pattern so divided that the laser beams may overlap on the site of lesion is conceivable. This modified laser irradiation device can allay the injury of the surface layer to a certain extent and heat the site of lesion to a sufficiently high temperature because it prevents a laser beam of unduly high output from impinging on the surface layer.
The laser irradiation device of this construction, however, allows no easy control of the depth of the position at which the laser beams emitted from the different laser emitting parts are converged (beam-condensing position). It, therefore, entails such problems as disabling application of uniform heat to the whole of the lesion, giving rise to local overheating or unduly insufficient heating, suffering the lesion to cause pain to the patient or involve complication, failing to manifest a fully satisfactory curing effect, and tending to incur relapse of the disease.
Further, this device by nature inevitably fixes the depth of the beam-condensing position at a constant distance. To change the depth of beam-condensing position to a necessary depth, therefore, it requires to exchange the laser irradiating device (laser probe) for a spare part having the depth of the beam-condensing position set in advance to the necessary distance.
When the depth of the beam-condensing position is altered by the exchange of the laser irradiation device, this alteration of the depth is barely attained stepwise and further brings such flaws as complicating the operation and increasing the load on the patient.
This invention, conceived in the light of the true state of prior art mentioned above, has for the object thereof the provision of a lateral-irradiation type laser irradiation device which is capable of effectively irradiating a target site (particularly at a considerable depth) with a laser beam while infallibly and easily preventing normal tissue from injury and a method for curing prostate gland by the use of the laser irradiation device.
According to this invention, since the laser beams emanating from a plurality of emitting parts are converged (condensed) via different routes on a target position and the energy densities of these laser beams are heightened at the target position and in the neighborhood thereof, the target site can be heated to a necessary temperature and the site (normal tissue) other than the target site can be held at a relatively low temperature. As a result, the injury possibly inflicted on the site other than the target site can be precluded completely or allayed markedly and, in particular, the safety of the patient can be secured.
According to this invention, since the target position can be moved by an emitting direction changing means, the whole of the target site can be uniformly heated to a necessary temperature while the site other than the target site is easily and infallibly retained at a relatively low temperature. Further, since the depth of the target position can be changed to an arbitrarily selected distance without requiring exchange of the laser irradiation device, the operation can be facilitated and the load on the patient can be alleviated.
Even when the inserting part of the laser irradiation device is barely capable of advancing halfway along the distance to a given body cavity, the device can heat the target site to a necessary temperature by irradiating the target site with laser beams. When the target site allows no easy transmission of laser beams or the laser beams for the irradiation have relatively low energy densities, the laser irradiation device is capable of irradiating the target site with laser beams while avoiding the site liable to involve complication.
According to the method of this invention, the inserting part of the laser irradiation device can be inserted from outside the body into a long slender lumen and the laser beams issued from a plurality of emitting parts can be passed through different routes and converged (condensed) on a target position and the energy densities of these laser beams can be heightened at the target position and in the neighborhood thereof. In the therapy of prostate gland, a disease in which a lesion exists at the end of a slender long urogenital canal, therefore, the method of this invention is highly effective in performing easily the therapy without exposing the patient to an undue load while precluding infliction of injury on the site other than the target site.